I'd had the TZ5 for a while before getting mine in May of last year, and I'd say they simply didn't increase the dial's stiffness to allow for it being exposed on the end of the camera, rather than safely near the middle - as it had been on the 5.

Very occasionally I still nudge it a notch or, worse, a half notch without noticing, but after the first week I never did press the
video button by mistake again - the other thing that seemed so awkward to begin with!